1. Field of the Invention
The invention is directed to a torsional vibration damper having a plurality of transmission elements which are rotatable relative to one another about a common axis of rotation.
2. Discussion of the Prior Art
German reference DE 41 28 868 discloses a torsional vibration damper having a transmission element on the drive side and a transmission element on the driven side which is rotatable relative to the drive-side transmission element against the action of a damping device. The damping device serves to transmit torque between the two transmission elements. The damping device has springs which are guided along a guide path via slide blocks and which serve as displaceable coupling bodies. A plurality of these springs are combined in a spring set which is in a working connection with one of the transmission elements at one end and with the other transmission element at the other end such that a deflection of one of the transmission elements in the circumferential direction by a relative movement of the coupling body results in a deflection of the other transmission element. Every coupling body is arranged in a recess of one of the transmission elements, which recess has the guide path, and is connected with a driver device of the other transmission element. The driver device is formed by the control element acting on the spring set.
Torsional vibration dampers according to the above-mentioned reference are suitable for filtering a complete frequency range, that is, for damping amplitudes of different orders. However, particularly troublesome amplitudes of a certain order cannot be effectively suppressed in the manner that is often required.
By constructing the coupling bodies as springs, it is ensured that the two transmission elements will be moved back into their initial position after every relative deflection brought about by a torsional vibration. Thus, the two transmission elements have an exactly defined reference position relative to one another in the unloaded state. However, a disadvantage in such coupling bodies is that the inertia which the corresponding transmission element sets in opposition to an introduced torsional vibration is not changeable. Furthermore, the constructional design of such a torsional vibration damper is relatively complicated, since control elements must be provided for the springs at both flywheel masses, the springs acting between these control elements.
A transmission element in the form of a flywheel mass is known from U.S. Pat. No. 5,295,411, in which a circular compensating flywheel mass is received in each of a plurality of circular cavities. The diameter of the compensating flywheel mass is smaller than that of the cavity. A flywheel mass of this type is commonly referred to as a Salomon or Solomon damper and has the advantage that the compensating flywheel masses are dependent on changes in speed at the flywheel mass with respect to their deflection speed. With a flywheel mass of this kind, torsional vibrations of a determined order, preferably of the second order in four-cylinder internal combustion engines, can be advantageously reduced by a determined amount at defined amplitude values; however, it is not possible to influence vibrations of another order. Further, wear can result in the running area of the compensating flywheel mass in the cavity or recess, so that the recess changes shape. This in turn influences the deflection behavior of the compensating flywheel mass and accordingly the damper behavior of the flywheel mass.
U.S. Pat. No. 2,205,401 shows another damper in which a flywheel mass having a guide path for damper masses which are in a working connection with an actuating or adjusting device is fastened to a drive, for example, a crankshaft. The damper masses, as well as the guide path associated therewith, have a curvature, preferably in a circular shape, wherein the radius of curvature of the damper masses is smaller than that of the associated guide paths so as to enable a rolling movement of the damper masses in the guide paths when torsional vibrations are introduced via the flywheel mass. The reason for the existence of a plurality of guide paths and the adjusting device mentioned above is so that the damper masses can be brought, during an adjusting process by the adjusting device, into the respective guide path required for damping a torsional vibration of a determined order occurring precisely at that time. Accordingly, in contrast to the damper discussed above in connection with U.S. Pat. No. 5,295,411, not only one order but a plurality of orders can be reduced by a determined amount. Nevertheless, there is again no possibility of influencing torsional vibrations of other orders. The problem of wear at the guide path discussed above also exists.